Numbering code for valves...

[KH Guitar Freak]

Ok, an update on my former thread. I've received the valves, and they seemed to be labelled "7600", and "32" and "29" respectively. Granted, the former pair of numbers represent the mA bias rating. But what does "7600" stand for???

 

[crane]

Plate votage ? :mrgreen:
Could be a resistance value or something like transconductance, don't know.
Could be an internal factory value/code too.

 

[dodger916]

Ok, an update on my former thread. I've received the valves, and they seemed to be labelled "7600", and "32" and "29" respectively. Granted, the former pair of numbers represent the mA bias rating. But what does "7600" stand for???

First, I'm assuming these are not color-coded Mesa tubes mentioned in the previous thread. What do you mean "labelled"? Is this factory stamped info or something the seller added to indicate the results of a tube tester? If seller-added, 7600 could represent mutual conductance, or a measure of how much life the tube has left. That seems like a good number, but you'll need to know the range for that particular tester for those type of tubes. 32 and 29 could be the plate current draw, not to be confused with plate voltage draw. A 30 watt 6L6 tube can handle plate voltages as high 500 volts, but most are in the 475 to 490 range.

 

[KH Guitar Freak]

Ok, an update on my former thread. I've received the valves, and they seemed to be labelled "7600", and "32" and "29" respectively. Granted, the former pair of numbers represent the mA bias rating. But what does "7600" stand for???

First, I'm assuming these are not color-coded Mesa tubes mentioned in the previous thread. What do you mean "labelled"? Is this factory stamped info or something the seller added to indicate the results of a tube tester? If seller-added, 7600 could represent mutual conductance, or a measure of how much life the tube has left. That seems like a good number, but you'll need to know the range for that particular tester for those type of tubes. 32 and 29 could be the plate current draw, not to be confused with plate voltage draw. A 30 watt 6L6 tube can handle plate voltages as high 500 volts, but most are in the 475 to 490 range.

The seller has the boxes of each valve labelled with "7600"...

 

[dodger916]

Ok, an update on my former thread. I've received the valves, and they seemed to be labelled "7600", and "32" and "29" respectively. Granted, the former pair of numbers represent the mA bias rating. But what does "7600" stand for???

First, I'm assuming these are not color-coded Mesa tubes mentioned in the previous thread. What do you mean "labelled"? Is this factory stamped info or something the seller added to indicate the results of a tube tester? If seller-added, 7600 could represent mutual conductance, or a measure of how much life the tube has left. That seems like a good number, but you'll need to know the range for that particular tester for those type of tubes. 32 and 29 could be the plate current draw, not to be confused with plate voltage draw. A 30 watt 6L6 tube can handle plate voltages as high 500 volts, but most are in the 475 to 490 range.

The seller has the boxes of each valve labelled with "7600"...

Probably mutual conductance. If they both read close to 7600, it DOES NOT indicate a matched duet (or quartet). Assuming 32 and 29 are the idle plate current draw (in milliamps), they are matched within about 10%. I've heard 5% is the number to reach for, but I've heard some say 10% is OK. Others can be more helpful here.

Here's something I picked up from another thread. I'm pretty sure he's talking about a Mark IIC+:
Stokes: "Simply put, the tubes that draw 20ma's will have a later breakup, the tubes that draw 30ma's will have a quicker breakup.Which is better? Only you can say,either tube will be "safe" in your amp."

 

[KH Guitar Freak]

Probably mutual conductance. If they both read close to 7600, it DOES NOT indicate a matched duet (or quartet). Assuming 32 and 29 are the idle plate current draw (in milliamps), they are matched within about 10%. I've heard 5% is the number to reach for, but I've heard some say 10% is OK. Others can be more helpful here.

Here's something I picked up from another thread. I'm pretty sure he's talking about a Mark IIC+:
Stokes: "Simply put, the tubes that draw 20ma's will have a later breakup, the tubes that draw 30ma's will have a quicker breakup.Which is better? Only you can say,either tube will be "safe" in your amp."

Oh, I probably didn't make myself clear. I have TWO sets of matched quads, the valves in a matched set all have a 32mA label, and the other set all have a 29mA label. I was basically interested in what the "7600" stands for. Cheers for the info...

 

[Ken j]

Probably "micromhos". This is the unit of measure that a Hickok tube tester uses to measure the value of a tube. For example a 6L6 needs a minimum reading of 3000 micromhos to be considered good.